1. Field of the Invention
The present invention relates to semiconductor devices, and more particularly, to a socket and a printed circuit board for semiconductor devices, and a method of testing semiconductor devices.
2. Description of the Related Art
Recent semiconductor devices operate at a high frequency band of several hundreds of MHz. In this high frequency band, the influence of the parasitic components of a semiconductor device package upon the operation of semiconductor devices increases. The parasitic components are resistance, inductance, and capacitance. To reduce these parasitic components, a chip scaled package (CSP) has been introduced The CSP is smaller than conventional plastic packages, so that the influence of the parasitic components of the CSP upon the operation of a semiconductor device is reduced.
A conventional CSP will now be described referring to FIGS. 1 and 2. FIG. 1 is a top plan view of a semiconductor device packaged by a conventional chip scaled package (CSP) method, and FIG. 2 is a cross-sectional view of the semiconductor device of FIG. 1 taken along line 2-2xe2x80x2.
A semiconductor device 11 is covered by a chip surface protective film 22 formed of polyamide or the like. In such a semiconductor device 11 packaged by a CSP method, balls 13 are connected to pads 15 via beam leads 17. The pads 15 are disposed in an area 19 that runs along the center of the semiconductor device 11, and the device is also covered by a tape 28 or the like.
Generally, the semiconductor device 11 packaged by the CSP method is mounted on a test socket to be tested. FIG. 3 is a top plan view of a conventional test socket, and FIGS. 4 and 5 are cross-sectional views of the test socket of FIG. 3 taken along lines 4-4xe2x80x2 and 5-5xe2x80x2, respectively.
Referring to FIGS. 3, 4 and 5, a conventional test socket 30 includes outer sidewalls 31 for fixing a semiconductor device 44 to be tested, an upper wall 45 and a lower supporting member 47. Also, the conventional test socket 30 includes ball contact springs 32, formed through the upper wall 45, which individually contact balls 43 connected to pads 53 via beam leads (not shown).
However, the semiconductor device 44 packaged by a CSP method has the balls 13 and the beam leads 17 formed thereon, as shown in FIGS. 1 and 2. Thus, even when a certain portion of the package is uncovered, the chip surface of the semiconductor device 44 cannot be directly accessed because of the balls 13 and the beam leads 17. Therefore, in contrast with general plastic packages, it is impossible to directly measure signal waveforms from the chip surface of a semiconductor device at a frequency where the semiconductor device operates.
To solve the above problem, it is an object of the present invention to provide a test socket capable of directly detecting waveforms from the chip surface of a semiconductor device packaged by a chip scaled package (CSP) method.
It is another object of the present invention to provide a printed circuit board (PCB) at which a test socket capable of directly detecting waveforms from the chip surface of a semiconductor device packaged by a CSP method is installed.
It is still another object of the present invention to provide a method of testing a semiconductor device capable of directly detecting waveforms from the chip surface of a semiconductor device packaged by a CSP method.
Accordingly, to achieve the first object, the present invention provides a socket for testing a semiconductor device, the socket including outer sidewalls, an upper wall and a lower support member for fixing the semiconductor device. The socket also includes ball contact springs, formed through the upper wall, which contact corresponding balls connected to the corresponding pads of a semiconductor device to be tested, and a socket aperture formed through the upper wall to expose the pads of the semiconductor device to the outside of the testing socket.
To achieve the second object, the present invention provides a printed circuit board at which a socket for testing a semiconductor device packaged by a CSP method is installed. The printed circuit board includes a board aperture formed over the socket aperture of the testing socket to expose the pads of a semiconductor device. Preferably, the upper wall of the testing socket is attached to the bottom of the printed circuit board. More preferably, the size and location of the socket aperture of the test socket are similar to those of the board aperture of the printed circuit board to expose the pads of a semiconductor device.
To achieve the third object, the present invention provides a method of testing a semiconductor device packaged by a CSP method, by which waveforms can be directly detected from the surface of a semiconductor device chip. The method includes: forming a socket aperture in a testing socket on which a semiconductor device to be tested is mounted; mounting the semiconductor device on the testing socket so that the pads of the semiconductor device are exposed through the socket aperture; forming a board aperture in a printed circuit board; attaching the testing socket to the bottom of the printed circuit board so that the socket aperture faces upward and is aligned vertically with the board aperture, whereby the pads of the semiconductor device are exposed through the socket aperture and the board aperture when the testing socket has been installed at the printed circuit board; and testing the semiconductor device through the board aperture and the socket aperture.
In the above-described devices and method of testing a semiconductor device, according to the present invention, the waveforms on the chip surface of a semiconductor device packaged by a CSP method can be directly detected.